Comparison of the ultrafast hot electron dynamics of titanium nitride and gold for plasmonic applications

Abstract

With similar optical properties to gold and high thermal stability, titanium nitride continues to prove itself as a promising plasmonic material for high-temperature applications in the visible and near-infrared. In this work, we use transient pump probe differential reflection measurements to compare the electron energy decay channels in titanium nitride and gold thin films. Using an extended two temperature model to incorporate the photoexcited electrons, it is possible to separate the electron-electron and electron-phonon scattering contributions immediately following the arrival of the pump pulse. This model allows for incredibly accurate determination of the internal electronic properties using only optical measurements. As the electronic properties are key in hot electron applications, we show that titanium nitide has substantially longer electron thermalization and electron-phonon scattering times. With this, we were also able to resolve electron thermal conduction in the film using purely optical measurements.

Plasmon-Enhanced Electron Harvesting in Robust Titanium Nitride Nanostructures

“…For semiconductors this is directly proportional to the free carrier density 29 ( ;< ). As we reported previously 8 , the differential signature of titanium oxynitride is dominated by the excited electrons in the conduction band of the TiO2x semiconducting oxide layer. Thus, the differential reflectivity is a straightforward parameter for comparing electron harvesting efficiencies between samples and geometries.…”

“…As shown in our previous work 8 , the surface oxide (semiconducting TiO2x) plays a determining role in the electron dynamics as it can harvest the photoexcited electrons in the underlying TiN layer and delay recombination for nanoseconds timescales. Following the patterning process, a surface oxide forms on the sidewalls of the TiN strips in addition to the top surface as shown schematically in Figure 1c.…”

“…As a preliminary investigation of the laser-induced changes to the material, we fit the measured data to a bi-exponential electron kinetic model proposed in our previous work 8 , which identifies the contribution of shallow and deep trap-mediated recombination. Details of the model are explained in Supplementary Section S2.…”

“…With broad, tunable resonances across the near-infrared, it shows superior photocatalytic performance to an equivalent gold system both in colloidal form 6 and deposited on semiconductor rods 7 , with advantages also for solar energy harvesting and photocatalysis. Perhaps the most exciting attribute of TiN is its semiconducting native oxide; our previous work 8 showed that electron harvesting into the omnipresent titania surface oxide layer could be effective (on the order of 10 $% '( for modest pump powers). Our previous work 4 used systematic material characterisation (XPS, spectroscopic ellipsometry) to investigate the underlying film and surface oxide layer properties of the materials used in this work.…”

Complementary Metal–Oxide–Semiconductor Compatible Deposition of Nanoscale Transition-Metal Nitride Thin Films for Plasmonic Applications

“…Real (a) and imaginary (b) spectroscopic ellipsometry data for TiN films deposited via HIPIMS onto glass and Si substrates. Figures include a comparison to literature values for TiN films. ,− (c) Figure of merit (−ε′/ε′′) (FOM) comparison of TiN thin films and literature data. References ,, and are deposited via RF magnetron sputtering at 850 °C, 600 °C, and RT, respectively.…”